BEST IN PHYSICS (IMAGING) - The Feasibility of An X-Ray Differential Phase Contrast Tomosynthesis System Adapted From a Clinical Digital Breast Tomosynthesis System

Purpose: This work aims to investigate the feasibility of a grating-based x-ray differential phase contrast (DPC) tomosynthesis imaging system based on an absorption-contrast DBT system currently available in the clinical practice. The main significance of this study is the potential improvement in lesion/calcification detection performance when the DPC mechanism is combined with the tomosynthesis imaging method.

Methods: First, a framework was developed to simultaneously reconstruct differential phase contrast (edge information), phase contrast (electron density information), and absorption contrast images. Second, a physical phantom and a benchtop DPC imaging system (40 kVp, 80 micron pixel pitch) were used to evaluate the reconstruction framework as well as the contrast improvement with the DPC mechanism. Third, a DPC system was designed based on the current hardware of a clinical absorption DBT system (Hologic Selenia Dimensions), and the task-based model observer detectability indices of the DPC tomosynthesis system were evaluated using a theoretical framework that quantitatively relates the noise properties of DPC-DBT with absorption DBT.

Results: Reconstructions of physical phantoms show improved signal difference to noise ratio (SDNR) compared with absorption images acquired under the same exposure (SDNR_PMMA = 5.9 and 0.6 for DPC and absorption, respectively). Equivalent spatial resolution for the two contrast mechanisms was observed from the line profiles and artifact spread functions of a bead. Design parameters of the DPC-DBT system are fully compatible with the current clinical system. The accuracy of the framework that predicts detectability in DPC-DBT was validated experimentally, and it suggests that the DPC mechanism will result in improved detectabilities of both small objects (e.g. calcification) and irregular-shaped objects (e.g. spiculated lesions).

Conclusion: It is feasible to build a DPC tomosynthesis system using the system setup of an existing clinical DBT system. The system shows promise in improving lesion and calcification detectability, and therefore merits further investigation.